Chapter 8 Sodium and Potassium

OVERVIEW

On average, the higher an individual's salt (sodium chloride) intake, the
higher an individual's blood pressure. Nearly all Americans consume
substantially more salt than they need. Decreasing salt intake is advisable to
reduce the risk of elevated blood pressure. Keeping blood pressure in the
normal range reduces an individual's risk of coronary heart disease, stroke,
congestive heart failure, and kidney disease. Many American adults will
develop hypertension (high blood pressure) during their lifetime. Lifestyle
changes can prevent or delay the onset of high blood pressure and can lower
elevated blood pressure. These changes include reducing salt intake,
increasing potassium intake, losing excess body weight, increasing physical
activity, and eating an overall healthful diet.

KEY RECOMMENDATIONS

Consume less than 2,300 mg (approximately 1 tsp of salt) of sodium
per day.

Choose and prepare foods with little salt. At the same time, consume
potassium-rich foods, such as fruits and vegetables.

Key Recommendations for Specific Population Groups

Individuals with hypertension, blacks, and middle-aged and older
adults. Aim to consume no more than 1,500 mg of sodium per day, and
meet the potassium recommendation (4,700 mg/day) with food.

DISCUSSION

Salt is sodium chloride. Food labels list sodium rather than salt content.
When reading a Nutrition Facts Panel on a food product, look for the sodium
content. Foods that are low in sodium (less than 140 mg or 5 percent of the
Daily Value [DV]) are low in salt.

Common sources of sodium found in the food supply are provided in
figure 4.
On average, the natural salt content of food accounts for only about 10
percent of total intake, while discretionary salt use (i.e., salt added at the
table or while cooking) provides another 5 to 10 percent of total intake.
Approximately 75 percent is derived from salt added by manufacturers. In
addition, foods served by food establishments may be high in sodium. It is
important to read the food label and determine the sodium content of food,
which can vary by several hundreds of milligrams in similar foods. For
example, the sodium content in regular tomato soup may be 700 mg per cup in
one brand and 1,100 mg per cup in another brand. Reading labels, comparing
sodium contents of foods, and purchasing the lower sodium brand may be one
strategy to lower total sodium intake (see table 15 for examples of these
foods).

An individual's preference for salt is not fixed. After consuming foods
lower in salt for a period of time, taste for salt tends to decrease. Use of
other flavorings may satisfy an individual's taste. While salt substitutes
containing potassium chloride may be useful for some individuals, they can be
harmful to people with certain medical conditions. These individuals should
consult a healthcare provider before trying salt substitutes.

Discretionary salt use is fairly stable, even when foods offered are lower
in sodium than typical foods consumed. When consumers are offered a lower
sodium product, they typically do not add table salt to compensate for the
lower sodium content, even when available. Therefore, any program for reducing
the salt consumption of a population should concentrate primarily on reducing
the salt used during food processing and on changes in food selection (e.g., more fresh,
less-processed items, less sodium-dense foods) and preparation.

Reducing salt intake is one of several ways that people may lower their
blood pressure. The relationship between salt intake and blood pressure is
direct and progressive without an apparent threshold. On average, the higher a
person's salt intake, the higher the blood pressure. Reducing blood pressure,
ideally to the normal range, reduces the risk of stroke, heart disease, heart
failure, and kidney disease.

Another dietary measure to lower blood pressure is to consume a diet rich
in potassium. A potassium-rich diet also blunts the effects of salt on blood
pressure, may reduce the risk of developing kidney stones, and possibly
decrease bone loss with age. The recommended intake of potassium for
adolescents and adults is 4,700 mg/day. Recommended intakes for potassium for
children 1 to 3 years of age is 3,000 mg/day, 4 to 8 years of age is 3,800
mg/day, and 9 to 13 years of age is 4,500 mg/day. Potassium should come
from food sources. Fruits and vegetables, which
are rich in potassium with its bicarbonate precursors, favorably affect
acid-base metabolism, which may reduce risk of kidney stones and bone loss.
Potassium-rich fruits and vegetables include leafy green vegetables, fruit
from vines, and root vegetables. Meat, milk, and cereal products also contain
potassium, but may not have the same effect on acid-base metabolism. Dietary
sources of potassium are listed in table 5 and
appendix B-1.

Considerations for Specific Population Groups

Individuals With Hypertension, Blacks, and Middle-Aged and Older Adults. Some
individuals tend to be more salt sensitive than others, including people with
hypertension, blacks, and middle-aged and older adults. Because blacks
commonly have a relatively low intake of potassium and a high prevalence of
elevated blood pressure and salt sensitivity, this population subgroup may
especially benefit from an increased dietary intake of potassium. Dietary
potassium can lower blood pressure and blunt the effects of salt on blood
pressure in some individuals. While salt substitutes containing potassium
chloride may be useful for some individuals, they can be harmful to people
with certain medical conditions. These individuals should consult a healthcare
provider before using salt substitutes.

FIGURE 4. The relative amounts of dietary sodium in the American diet.
a

The ranges of sodium content for selected foods available in the retail
market. This table is provided to exemplify the importance of reading the food
label to determine the sodium content of food, which can vary by several
hundreds of milligrams in similar foods.

Source: Agricultural Research Service Nutrient
Database for Standard Reference, Release 17 and recent manufacturers label
data from retail market surveys. Serving sizes were standardized to be
comparable among brands within a food. Pizza and bread slices vary in size and
weight across brands.